diff --git a/packages/knowledge-base/Classes/Controller/BackendKnowledgeBaseController.php b/packages/knowledge-base/Classes/Controller/BackendKnowledgeBaseController.php
index dcdc9ea..3e4d514 100644
--- a/packages/knowledge-base/Classes/Controller/BackendKnowledgeBaseController.php
+++ b/packages/knowledge-base/Classes/Controller/BackendKnowledgeBaseController.php
@@ -53,8 +53,6 @@ public function indexAction(): ResponseInterface
         $this->moduleTemplate->assign('openDocumentId', $openDocumentId);
         $loadChildrenUrl = $this->uriBuilder->reset()->uriFor('loadDocumentChildren', ['documentUid' => 'DOCUMENT_ID_PLACEHOLDER']);
         $this->moduleTemplate->assign('loadChildrenUrl', $loadChildrenUrl);
-        $this->moduleTemplate->assign('semanticSearchAvailable', $this->modelAvailabilityService->isEmbeddingServerAvailable());
-        $this->moduleTemplate->assign('ragSearchAvailable', $this->modelAvailabilityService->isGenerationServerAvailable());
         return $this->moduleTemplate->renderResponse('Backend/Index');
     }
 
@@ -133,6 +131,22 @@ public function createAction(string $documentHeadline, int $parentId = 0, string
         return $this->redirect('index', null, null, ['openDocumentId' => $result['documentUid']]);
     }
 
+    public function ajaxCheckAvailabilityAction(ServerRequest $request): ResponseInterface
+    {
+        $service = $request->getQueryParams()['service'] ?? '';
+
+        $result = match($service) {
+            'semantic' => ['available' => $this->modelAvailabilityService->isEmbeddingServerAvailable()],
+            'rag'      => ['available' => $this->modelAvailabilityService->isGenerationServerAvailable()],
+            default    => [
+                'semantic' => $this->modelAvailabilityService->isEmbeddingServerAvailable(),
+                'rag'      => $this->modelAvailabilityService->isGenerationServerAvailable(),
+            ],
+        };
+
+        return $this->jsonResponse((string)json_encode($result));
+    }
+
     public function ajaxLoadDocumentAction(ServerRequest $request): ResponseInterface
     {
         $params = $request->getQueryParams();
diff --git a/packages/knowledge-base/Configuration/Backend/AjaxRoutes.php b/packages/knowledge-base/Configuration/Backend/AjaxRoutes.php
index 6a27543..246f33e 100644
--- a/packages/knowledge-base/Configuration/Backend/AjaxRoutes.php
+++ b/packages/knowledge-base/Configuration/Backend/AjaxRoutes.php
@@ -17,4 +17,8 @@
         'path' => '/knowledgebase/searchDocuments',
         'target' => BackendKnowledgeBaseController::class . '::ajaxSearchAction',
     ],
+    'checkAvailability' => [
+        'path' => '/knowledgebase/checkAvailability',
+        'target' => BackendKnowledgeBaseController::class . '::ajaxCheckAvailabilityAction',
+    ],
 ];
diff --git a/packages/knowledge-base/Resources/Public/Css/Search.css b/packages/knowledge-base/Resources/Public/Css/Search.css
index 16f2f1c..a166745 100644
--- a/packages/knowledge-base/Resources/Public/Css/Search.css
+++ b/packages/knowledge-base/Resources/Public/Css/Search.css
@@ -89,6 +89,16 @@
     background: rgba(255, 135, 0, 0.06);
 }
 
+.kb-flyout-mode-btn:disabled {
+    opacity: 0.35;
+    cursor: not-allowed;
+}
+
+.kb-flyout-mode-btn:disabled:hover {
+    background: transparent;
+    color: #6b6b6b;
+}
+
 /* Flyout status (loading / error) */
 .kb-flyout-status {
     padding: 10px 12px;
diff --git a/packages/knowledge-base/Resources/Public/JavaScript/Searchbar.js b/packages/knowledge-base/Resources/Public/JavaScript/Searchbar.js
index ae9acf2..45ea1ea 100644
--- a/packages/knowledge-base/Resources/Public/JavaScript/Searchbar.js
+++ b/packages/knowledge-base/Resources/Public/JavaScript/Searchbar.js
@@ -30,6 +30,7 @@ class KnowledgeBaseSearchBar {
         this.iconBoard = document.getElementById('kb-icon-board')?.innerHTML ?? '';
 
         this.bindEvents();
+        this.checkAvailability();
     }
 
     bindEvents() {
@@ -75,6 +76,36 @@ class KnowledgeBaseSearchBar {
         this.form.addEventListener('submit', e => e.preventDefault());
     }
 
+    async checkAvailability() {
+        const base = TYPO3?.settings?.ajaxUrls?.checkAvailability;
+        if (!base) return;
+
+        const check = async (service) => {
+            try {
+                const response = await fetch(`${base}&service=${service}`, {
+                    headers: { 'X-Requested-With': 'XMLHttpRequest' },
+                });
+                if (!response.ok) return true;
+                const data = await response.json();
+                return data.available !== false;
+            } catch {
+                return true; // leave enabled if check fails
+            }
+        };
+
+        const [semanticOk, ragOk] = await Promise.all([check('semantic'), check('rag')]);
+
+        this.modeButtons.forEach(btn => {
+            if (btn.dataset.mode === 'semantic' && !semanticOk) {
+                btn.disabled = true;
+                btn.title = 'Semantic search server unavailable';
+            } else if (btn.dataset.mode === 'rag' && !ragOk) {
+                btn.disabled = true;
+                btn.title = 'RAG search server unavailable';
+            }
+        });
+    }
+
     openFlyout() {
         this.flyout.classList.add('is-open');
     }